X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;ds=sidebyside;f=lib%2FCodeGen%2FPrologEpilogInserter.cpp;h=e7b712d4b2598e3607ce4ebb82dadcd7e158da81;hb=69300a2f47541a32cf453c857b2a6075c0c65632;hp=d573e91a4416fa5247a1e8f862a2d02409b0d269;hpb=6627ac040a14f3a79564fd6ec030f9361f81d20e;p=oota-llvm.git diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp index d573e91a441..e7b712d4b25 100644 --- a/lib/CodeGen/PrologEpilogInserter.cpp +++ b/lib/CodeGen/PrologEpilogInserter.cpp @@ -19,6 +19,7 @@ // //===----------------------------------------------------------------------===// +#define DEBUG_TYPE "pei" #include "PrologEpilogInserter.h" #include "llvm/CodeGen/MachineDominators.h" #include "llvm/CodeGen/MachineLoopInfo.h" @@ -32,7 +33,10 @@ #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Compiler.h" +#include "llvm/Support/Debug.h" #include "llvm/ADT/IndexedMap.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" #include @@ -40,8 +44,15 @@ using namespace llvm; char PEI::ID = 0; -static RegisterPass -X("prologepilog", "Prologue/Epilogue Insertion"); +INITIALIZE_PASS_BEGIN(PEI, "prologepilog", + "Prologue/Epilogue Insertion", false, false) +INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) +INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) +INITIALIZE_PASS_END(PEI, "prologepilog", + "Prologue/Epilogue Insertion", false, false) + +STATISTIC(NumVirtualFrameRegs, "Number of virtual frame regs encountered"); +STATISTIC(NumScavengedRegs, "Number of frame index regs scavenged"); /// createPrologEpilogCodeInserter - This function returns a pass that inserts /// prolog and epilog code, and eliminates abstract frame references. @@ -56,7 +67,6 @@ bool PEI::runOnMachineFunction(MachineFunction &Fn) { const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL; FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn); - FrameConstantRegMap.clear(); // Calculate the MaxCallFrameSize and AdjustsStack variables for the // function's frame information. Also eliminates call frame pseudo @@ -72,10 +82,10 @@ bool PEI::runOnMachineFunction(MachineFunction &Fn) { calculateCalleeSavedRegisters(Fn); // Determine placement of CSR spill/restore code: - // - with shrink wrapping, place spills and restores to tightly + // - With shrink wrapping, place spills and restores to tightly // enclose regions in the Machine CFG of the function where - // they are used. Without shrink wrapping - // - default (no shrink wrapping), place all spills in the + // they are used. + // - Without shink wrapping (default), place all spills in the // entry block, all restores in return blocks. placeCSRSpillsAndRestores(Fn); @@ -260,8 +270,7 @@ void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) { if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx; } else { // Spill it to the stack where we must. - FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, - true, false); + FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true); } I->setFrameIdx(FrameIdx); @@ -462,8 +471,10 @@ AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, Offset = (Offset + Align - 1) / Align * Align; if (StackGrowsDown) { + DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n"); MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset } else { + DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n"); MFI->setObjectOffset(FrameIdx, Offset); Offset += MFI->getObjectSize(FrameIdx); } @@ -548,15 +559,66 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign); } + // FIXME: Once this is working, then enable flag will change to a target + // check for whether the frame is large enough to want to use virtual + // frame index registers. Functions which don't want/need this optimization + // will continue to use the existing code path. + if (MFI->getUseLocalStackAllocationBlock()) { + unsigned Align = MFI->getLocalFrameMaxAlign(); + + // Adjust to alignment boundary. + Offset = (Offset + Align - 1) / Align * Align; + + DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n"); + + // Resolve offsets for objects in the local block. + for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) { + std::pair Entry = MFI->getLocalFrameObjectMap(i); + int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second; + DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" << + FIOffset << "]\n"); + MFI->setObjectOffset(Entry.first, FIOffset); + } + // Allocate the local block + Offset += MFI->getLocalFrameSize(); + + MaxAlign = std::max(Align, MaxAlign); + } + // Make sure that the stack protector comes before the local variables on the // stack. - if (MFI->getStackProtectorIndex() >= 0) + SmallSet LargeStackObjs; + if (MFI->getStackProtectorIndex() >= 0) { AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown, Offset, MaxAlign); + // Assign large stack objects first. + for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) { + if (MFI->isObjectPreAllocated(i) && + MFI->getUseLocalStackAllocationBlock()) + continue; + if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) + continue; + if (RS && (int)i == RS->getScavengingFrameIndex()) + continue; + if (MFI->isDeadObjectIndex(i)) + continue; + if (MFI->getStackProtectorIndex() == (int)i) + continue; + if (!MFI->MayNeedStackProtector(i)) + continue; + + AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign); + LargeStackObjs.insert(i); + } + } + // Then assign frame offsets to stack objects that are not used to spill // callee saved registers. for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) { + if (MFI->isObjectPreAllocated(i) && + MFI->getUseLocalStackAllocationBlock()) + continue; if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) continue; if (RS && (int)i == RS->getScavengingFrameIndex()) @@ -565,6 +627,8 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { continue; if (MFI->getStackProtectorIndex() == (int)i) continue; + if (LargeStackObjs.count(i)) + continue; AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign); } @@ -695,16 +759,8 @@ void PEI::replaceFrameIndices(MachineFunction &Fn) { // If this instruction has a FrameIndex operand, we need to // use that target machine register info object to eliminate // it. - TargetRegisterInfo::FrameIndexValue Value; - unsigned VReg = - TRI.eliminateFrameIndex(MI, SPAdj, &Value, - FrameIndexVirtualScavenging ? NULL : RS); - if (VReg) { - assert (FrameIndexVirtualScavenging && - "Not scavenging, but virtual returned from " - "eliminateFrameIndex()!"); - FrameConstantRegMap[VReg] = FrameConstantEntry(Value, SPAdj); - } + TRI.eliminateFrameIndex(MI, SPAdj, + FrameIndexVirtualScavenging ? NULL : RS); // Reset the iterator if we were at the beginning of the BB. if (AtBeginning) { @@ -732,38 +788,6 @@ void PEI::replaceFrameIndices(MachineFunction &Fn) { } } -/// findLastUseReg - find the killing use of the specified register within -/// the instruciton range. Return the operand number of the kill in Operand. -static MachineBasicBlock::iterator -findLastUseReg(MachineBasicBlock::iterator I, MachineBasicBlock::iterator ME, - unsigned Reg) { - // Scan forward to find the last use of this virtual register - for (++I; I != ME; ++I) { - MachineInstr *MI = I; - bool isDefInsn = false; - bool isKillInsn = false; - for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) - if (MI->getOperand(i).isReg()) { - unsigned OpReg = MI->getOperand(i).getReg(); - if (OpReg == 0 || !TargetRegisterInfo::isVirtualRegister(OpReg)) - continue; - assert (OpReg == Reg - && "overlapping use of scavenged index register!"); - // If this is the killing use, we have a candidate. - if (MI->getOperand(i).isKill()) - isKillInsn = true; - else if (MI->getOperand(i).isDef()) - isDefInsn = true; - } - if (isKillInsn && !isDefInsn) - return I; - } - // If we hit the end of the basic block, there was no kill of - // the virtual register, which is wrong. - assert (0 && "scavenged index register never killed!"); - return ME; -} - /// scavengeFrameVirtualRegs - Replace all frame index virtual registers /// with physical registers. Use the register scavenger to find an /// appropriate register to use. @@ -773,27 +797,14 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) { E = Fn.end(); BB != E; ++BB) { RS->enterBasicBlock(BB); - // FIXME: The logic flow in this function is still too convoluted. - // It needs a cleanup refactoring. Do that in preparation for tracking - // more than one scratch register value and using ranges to find - // available scratch registers. - unsigned CurrentVirtReg = 0; - unsigned CurrentScratchReg = 0; - bool havePrevValue = false; - TargetRegisterInfo::FrameIndexValue PrevValue(0,0); - TargetRegisterInfo::FrameIndexValue Value(0,0); - MachineInstr *PrevLastUseMI = NULL; - unsigned PrevLastUseOp = 0; - bool trackingCurrentValue = false; + unsigned VirtReg = 0; + unsigned ScratchReg = 0; int SPAdj = 0; // The instruction stream may change in the loop, so check BB->end() // directly. for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { MachineInstr *MI = I; - bool isDefInsn = false; - bool isKillInsn = false; - bool clobbersScratchReg = false; bool DoIncr = true; for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { if (MI->getOperand(i).isReg()) { @@ -801,125 +812,30 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) { unsigned Reg = MO.getReg(); if (Reg == 0) continue; - if (!TargetRegisterInfo::isVirtualRegister(Reg)) { - // If we have a previous scratch reg, check and see if anything - // here kills whatever value is in there. - if (Reg == CurrentScratchReg) { - if (MO.isUse()) { - // Two-address operands implicitly kill - if (MO.isKill() || MI->isRegTiedToDefOperand(i)) - clobbersScratchReg = true; - } else { - assert (MO.isDef()); - clobbersScratchReg = true; - } - } + if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue; - } - // If this is a def, remember that this insn defines the value. - // This lets us properly consider insns which re-use the scratch - // register, such as r2 = sub r2, #imm, in the middle of the - // scratch range. - if (MO.isDef()) - isDefInsn = true; + + ++NumVirtualFrameRegs; // Have we already allocated a scratch register for this virtual? - if (Reg != CurrentVirtReg) { + if (Reg != VirtReg) { // When we first encounter a new virtual register, it // must be a definition. assert(MI->getOperand(i).isDef() && "frame index virtual missing def!"); - // We can't have nested virtual register live ranges because - // there's only a guarantee of one scavenged register at a time. - assert (CurrentVirtReg == 0 && - "overlapping frame index virtual registers!"); - - // If the target gave us information about what's in the register, - // we can use that to re-use scratch regs. - DenseMap::iterator Entry = - FrameConstantRegMap.find(Reg); - trackingCurrentValue = Entry != FrameConstantRegMap.end(); - if (trackingCurrentValue) { - SPAdj = (*Entry).second.second; - Value = (*Entry).second.first; - } else { - SPAdj = 0; - Value.first = 0; - Value.second = 0; - } - - // If the scratch register from the last allocation is still - // available, see if the value matches. If it does, just re-use it. - if (trackingCurrentValue && havePrevValue && PrevValue == Value) { - // FIXME: This assumes that the instructions in the live range - // for the virtual register are exclusively for the purpose - // of populating the value in the register. That's reasonable - // for these frame index registers, but it's still a very, very - // strong assumption. rdar://7322732. Better would be to - // explicitly check each instruction in the range for references - // to the virtual register. Only delete those insns that - // touch the virtual register. - - // Find the last use of the new virtual register. Remove all - // instruction between here and there, and update the current - // instruction to reference the last use insn instead. - MachineBasicBlock::iterator LastUseMI = - findLastUseReg(I, BB->end(), Reg); - - // Remove all instructions up 'til the last use, since they're - // just calculating the value we already have. - BB->erase(I, LastUseMI); - I = LastUseMI; - - // Extend the live range of the scratch register - PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false); - RS->setUsed(CurrentScratchReg); - CurrentVirtReg = Reg; - - // We deleted the instruction we were scanning the operands of. - // Jump back to the instruction iterator loop. Don't increment - // past this instruction since we updated the iterator already. - DoIncr = false; - break; - } - // Scavenge a new scratch register - CurrentVirtReg = Reg; + VirtReg = Reg; const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg); - CurrentScratchReg = RS->FindUnusedReg(RC); - if (CurrentScratchReg == 0) - // No register is "free". Scavenge a register. - CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj); - - PrevValue = Value; + ScratchReg = RS->scavengeRegister(RC, I, SPAdj); + ++NumScavengedRegs; } - // replace this reference to the virtual register with the + // Replace this reference to the virtual register with the // scratch register. - assert (CurrentScratchReg && "Missing scratch register!"); - MI->getOperand(i).setReg(CurrentScratchReg); + assert (ScratchReg && "Missing scratch register!"); + MI->getOperand(i).setReg(ScratchReg); - if (MI->getOperand(i).isKill()) { - isKillInsn = true; - PrevLastUseOp = i; - PrevLastUseMI = MI; - } } } - // If this is the last use of the scratch, stop tracking it. The - // last use will be a kill operand in an instruction that does - // not also define the scratch register. - if (isKillInsn && !isDefInsn) { - CurrentVirtReg = 0; - havePrevValue = trackingCurrentValue; - } - // Similarly, notice if instruction clobbered the value in the - // register we're tracking for possible later reuse. This is noted - // above, but enforced here since the value is still live while we - // process the rest of the operands of the instruction. - if (clobbersScratchReg) { - havePrevValue = false; - CurrentScratchReg = 0; - } if (DoIncr) { RS->forward(I); ++I;